Alien Invaders and Mermaids’ Purses
21 May 2009 2 person/people have discussed this topic.A seashore survey workshop in Cardigan Bay, 6th June 2009
Wildlife in our seas and on our shores is under pressure from a variety of causes. Animals and plants from the other side of the world have been accidentally introduced and are spreading around the coast, threatening to out-compete native wildlife. Many fish are becoming increasingly rare because of over fishing, habitat damage and climate change. The once common skate is now commercially extinct in the Irish Sea.
We know far less about life below the waves than on land and have much still to learn. Come along and find out how you can help us to monitor some of these changes. After a brief introductory session we will be splitting up into three groups to survey the shore at New Quay, Cei Bach and Gilfach yr Halen for wireweed (an invasive seaweed from the Pacific) and looking for other invasive species and mermaids’ purses (egg cases of skates and rays). We will also be looking for animals and plants that can help us to see the effects of climate change.
The event is free and open to all. We especially welcome people who might be willing to adopt their local beach for regular egg case surveys and searches for invasive species.
Meet in the parking field next to Cei Bach Country Club at 12.30pm (1.5 miles east of New Quay, grid ref SN 409 596 - follow the signs to Cei Bach and then to the beach, parking £1). Bring wellies or other grippy shoes you don’t mind getting wet, sun hats and lotion (or rain coats as appropriate!), a packed lunch (or eat early!) and a clip board if you have one.
Any questions? call Ben Sampson on 01545 572139 or Jenny Higgins on 01970 821126
2 Comments
Vickie Hickin on June 3rd, 2009
Hello,
The explosion of spider crabs occured quite a few years ago in Cardigan Bay, becoming a real pest to lobster fishermen by crowding pots and excluding lobsters. As a result a market developed for them and they are still sold on. Prices decrease as the market floods and later in the season they may be sold for bait. The large increase in scallop dredging in Cardigan Bay has occurred in the last couple of years and if anything could be more likely to have a detrimental effect on spider crab populations due to their diet.
Spider crabs have a varied diet, eating both algae and benthic invertebrates. They prefer prey that does not move around, which means they will use less energy in predation. A study linked their diet to the moult cycle which is also when crabs mate (whilst the female shell is soft).
Spider crabs do aggregate in large numbers, known as ‘podding’ but conditions for this vary.
In summary: it is most unlikely that scallop dredging has caused an explosion of spider crabs.
Hope this helps.
Vickie Hickin
Biodiversity Officer
North Western and North Wales Sea Fisheries Committee
John Noble on June 2nd, 2009
Dear Sir,
Is there any connection between the population explosion if spider crabs and the destruction of life bt the Scallop Boats in Cardigan Bay?
I am staying at the home of a many generations son of Borth who took us crab and prawn collecting on the rocks here. He noticed unusually large numbers of the crabs and was puzzled by this. Are the spiders detritus feeders and could there be a conection with scallop seabed/life destruction?.
John Noble